libdap: 3.19.1 -> 3.20.0

* libdap: 3.19.1 -> 3.20.0 (#47785)

Semi-automatic update generated by
https://github.com/ryantm/nixpkgs-update tools. This update was made
based on information from
https://repology.org/metapackage/libdap/versions

* libdap: homepage has moved